Add .readthedocs.yaml and set specific versions of sphinx and sphinx_…

…rtd_theme in requirements.txt (#177)

.readthedocs.yaml

@@ -0,0 +1,23 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required 
+version: 2
+
+# Build all formats (htmlzip, pdf, epub)
+#formats: all
+formats: []
+
+# Optionally set the version of Python and requirements required to build your
+# docs
+python:
+   version: 3.7
+   install:
+   - requirements: docs/UsersGuide/requirements.txt
+
+# Configuration for Sphinx documentation (this is the default documentation
+# type)
+sphinx:
+  builder: html
+  configuration: docs/UsersGuide/source/conf.py

docs/UsersGuide/requirements.txt

@@ -1,2 +1,3 @@
+sphinx==2.4.4
 sphinxcontrib-bibtex
-sphinx_rtd_theme
+sphinx-rtd-theme==0.4.3